Dynamoelectric machines, such as motors, typically include a rotatable rotor and a shaft extending outwardly from at least one end of the rotor. The shaft is mounted to the rotor so that the rotation axis of the shaft is coaxial with the axis of rotation of the rotor. The shaft extends from the rotor and through an opening formed in the motor end plate. Typically, a bearing is mounted in the end plate and supports the shaft.
Alignment between the shaft and the bearing is important in that misalignment could disturb operation of the motor, including rendering the motor inoperable. For example, during normal operation, a hydrodynamic lubricating film is formed between the bearing and shaft by oil supplied from an oil wick. If side forces or other forces cause misalignment between the bearing and the shaft, the film could be disrupted. As a result, metal-to-metal contact can be made between the bearing and the shaft. Such metal-to-metal contact, of course, is highly undesirable.
Various types of bearing systems have been developed to control the amount of radial movement of the rotating rotor portion, and to provide a lubricated surface about which the shaft rotates. One such bearing assembly is disclosed in U.S. Pat. No. 5,677,584 to Keck, which patent is commonly assigned herewith and is incorporated herein by reference.
While a bearing assembly such as that disclosed in the above-referenced Keck patent works well for its intended fuiction, there are often times when the rotor requires axial alignment and support in order to prevent "thrust" from axially dislocating the rotor relative to the motor stator. Such axial pulsations of the rotor can result in, among other things, objectionable motor noises.
A number of thrust compensating arrangements have been developed to address this axial thrust problem. However, none of these thrust compensating arrangements address the radial bearing alignment function. In one arrangement that is configured to suppress only thrust fluctuations, a "three-spoke" spring element is configured with unidirectional arcuate spring arms that extend from each of the ends of the spokes. Although such an arrangement suppresses fluctuation of thrust loads, it does not in any way function to prevent radial movement of the rotating element. Viewed another way, such a spring does not enhance axial alignment and retention of the bearing in the bearing seat.
Another known configuration includes a securing ring having a relatively large opening in the center thereof to accommodate the motor shaft. The ring includes one or more surfaces to support the rotating motor element. The inner portion of the ring is interrupted by a plurality of slots and securing fingers to provide axial support. Again, while "thrust-suppression" is provided, there still exists the potential for the rotor to shift radially and, thus damage the rotor and stator.
Accordingly, there continues to be a need for a one-piece bearing retention element that includes an integral thrust surface for use with dynamoelectric machines. Such a bearing retention member provides a dual rate spring for providing different support forces for maintaining the motor bearing in its seat, while simultaneously providing "thrust" compensating or accommodating forces.